Like the other posters, my language is set on ‘French’ and my region on ‘France’.
I have the same issue, that is Cmd+I and Cmd+B not working. Cmd+U works.
The same ‘workaround’ works : making Scrivener an English app in ‘Langage and region’
Nota : I had the same issue with Scapple when I switched to Catalina (I posted that on the forum) but the problem just ‘disappeared’ on Thur 24 Oct (if I remember correctly) and Scapple works fine now…
I don’t know whether it is related to this issue. I use Alfred. When typing ‘Scapple’ or ‘Scrivener’ now, I’ve got those results since recently :
As weird as that is, I don’t think that would cause a permission problem. Reason being, the /System/Volumes/Data file is a hard link to the root level of the operating system, meaning everything inside that folder is a mirror copy of the original. Thus, if you accidentally launch a program through its mirror copy in that path, it is the identical copy found in /Applications—which means if it can update itself it will update whether you launch it through /Applications or /System/Volumes/Data/Applications. If that makes no sense, think of it like Collections in Scrivener. You can list a piece of text twice, but if you edit it you edit the original words, whether you load it from the Binder or the collection.
Now as to why Apple has saw fit to create a hard link to the root level of the disk is beyond me! On the surface that seems like a really dumb thing to do, but I’m sure they have some reason to necessitate accessing data through that path instead of just using the root itself.
As for Butler, you might want to blacklist that Data path to avoid the index listing things twice.
Interesting. I did not know this option. Thx 
NB : the new Alfred (4) displays the app names only once. I’ve just updated it from Alfred 3 (free version).